2 beers, same yeast, krausen explosion

I have an IPA and a pale ale in my fermentation fridge as we speak.
Both beers have Wyeast 1056 activator @ 68F.
the IPA got a nice krausen ring but nothing explosive or ridiculous.
The pale ale has clogged the airlock twice now because the krausen was all the way up the neck of the carboy.
I used a starter for the IPA. I did not use one for the pale ale.
Anyone have any input on why the pale ale went nuts while the IPA (with starter) did not?
Thanks all.
Dustin

The yeast might have had an easier time adjusting to the lower OG of the Pale. Also, I'd think there are other factors that might contribute to epic-blowoff-krauesen formation besides yeat activity levels -- higher levels of protein in the wort, etc.